1. Field of the Invention
The present invention relates to a piping connector preferably used in a fluid pipe in, for example, a cooling system or an intake system of an engine of an automobile.
2. Description of the Related Art
In connecting to, for example, a radiator hose or the like of an automobile, there is widely utilized a piping connector (pipe joint) made to be connected in one touch motion by only inserting a plug attached to an end portion of other pipe into a socket attached to an end portion of one pipe.
For example, in JP-A-10-9470, there is disclosed such a piping connector in which an outer peripheral groove is provided at an outer periphery of a female pipe (socket), the outer peripheral grove is provided with notched grooves penetrating inner and outer diameters and opposed to each other by a necessary angle, a stop piece arm (stopper) is engaged with a valley peripheral diameter portion of an unnotched groove portion, respective locking arms extended from the stop piece arm are made to span the respective notched grooves to lock, and portions of the respective locking arms are projected into the female pipe and fit to a groove at an outer periphery of a male pipe (plug).
According to such a piping connector, in order to facilitate the stopper projected to an inner periphery of the socket through the notched groove of the socket to engage with the groove at the outer periphery of the plug, the plug is formed with a taper wall for guiding the stopper to the groove.
A seal ring is arranged between an inner periphery of the socket and an outer periphery of the plug in order to seal in airtight such that a fluid flowing at inside of a pipe does not leak in a state of connecting the connector.
Further, in order to facilitate to insert a front end of the plug into the socket, insert the front end of the plug into the seal ring and fit the stopper to the groove of the plug, the plug is provided with a first taper portion, a flat portion, and a second taper portion continuously from a side of the front end in a sectional shape along an axial direction thereof.
In this case, the first taper portion is operated to facilitate to insert the front end of the plug into the seal ring, the flat portion is arranged with the seal ring at an outer periphery thereof and operated to seal an interval between the outer periphery of the flat portion and the inner periphery of the socket in airtight, and the second taper portion is operated as a guide face for expanding a diameter of the stopper to drop to the groove of the plug.
However, according to the piping connector of the prior art, in a procedure of inserting the plug into the socket, before the seal ring passes a portion of shifting from the first taper portion to the flat portion, the diameter of the stopper is expanded while being brought into contact with the second taper portion and therefore, there poses a problem that an inserting resistance becomes extremely large.
That is, FIG. 5 illustrates an inserting resistance A brought about by the seal ring, and an inserting resistance B brought about by the stopper, and an inserting resistance C as a whole including a total thereof.
When the seal ring passes the portion shifting from the first taper portion to the flat portion, the inserting resistance becomes a curve constituting a peak by a dotted line X in the drawing. When the seal ring rides over the flat portion from the first taper portion, the inserting resistance A is rapidly reduced and finally becomes substantially a constant value.
In contrast thereto, the inserting resistance B in accordance with rise thereof while the stopper is being brought into contact with the second taper portion to expand the diameter, is generated before the inserting resistance A by the seal ring constitutes the peak and is gradually increased and constitutes a peak at a portion thereof indicated by a dotted line Y in the drawing which is slightly retarded from the peak of the inserting resistance A.
As a result, the inserting resistance C as a hole including the total constitutes a peak at a position X substantially overlapping the peak of the inserting resistance A and a magnitude thereof becomes the inserting resistance A+the inserting resistance B at the position X and therefore, the magnitude is considerably increased by adding the both resistances.
Since the inserting resistance is large as described above, the plug needs to be pressed into the socket by a strong force, which may constitute a hindrance when operation is carried out by putting the hand into a narrow gap arranged with an engine of an automobile or the like.